Theme: Homophones. Five of them; enough for a limerick, eh?
17A. Legendary terror of the deep: SEA MONSTER
36A. Honor roll student's disappointment: C-PLUS
54A. "Doesn't matter to me": "SEE IF I CARE"
11D. "Forget You" singer who was a coach on "The Voice": CEE LO GREEN
27D. "Aye, lass," in Acapulco: "SI, SENORITA"
Argyle here. That last one; I picture Scotty from Star Trek beamed down into Mexico. A nice mix of wheelhouses in a classic pinwheel grid. Several CSO's.
1. Pet adoption agcy.: SPCA. (Society for the Prevention of Cruelty to Animals)
5. West Indies tribe for which a sea is named: CARIB. Doubling the ending 'b' of Carib and adding -ean makes it an adjective, Caribbean Sea, as well as a noun.
10. "Rhyme Pays" rapper: ICE-T. This is the intro to his "Rhyme Pays" album, here.(6:30)
14. Boxers Laila and Muhammad: ALIs
15. Carne __: burrito filling: ASADA
16. Benelux country: Abbr.: NETH. (Netherlands) Benelux is the union Belgium, the Netherlands, and Luxembourg.
19. __ blocker: BETA
20. Action hero Jason in three Ludlum novels: BOURNE. The Bourne Identity, The Bourne Supremacy, The Bourne Ultimatum
21. Swedish vodka brand: ABSOLUT
23. Material: CLOTH
25. Prefix with space: AERO
26. "__ the Sheriff": Clapton hit: I SHOT. Live(8:28)
28. Under threat: IN DANGER
32. Like most people: ASIAN
33. Comic's perch: STOOL
34. Label for Elvis: RCA
35. "Supervixens" director Meyer: RUSS. Sexploitation films.
37. Fashion line: SEAM. Easy to overthink it.
38. Author's ending?: IZE. (authorize) Good misdirection.
39. Celebrated chef Ducasse: ALAIN. French.
40. Copycats: APERS
41. Lovers of wordplay: PUNSTERS
43. Get big on Twitter: TREND
44. Gumbo pod: OKRA
45. Sierra Nevada lake: TAHOE
47. Ginger's "Gilligan's Island" hutmate: MARY ANN. (Dawn Wells)
50. Repaired, as a fence: MENDED
53. Awesome, nowadays: EPIC
57. Old film dog: ASTA. (Skippy)
58. "Family Matters" misfit: URKEL. (Jaleel White)
59. Mirror shape: OVAL
60. Quantum movement?: LEAP. It was a TV Series (1989–1993).
61. Body of verse: POESY
62. Sunday benches: PEWS
1. Airline to Oslo: SAS. (Originally an abbreviation of its former name Scandinavian Airlines System or legally Scandinavian Airlines System Denmark–Norway–Sweden)
2. Working-class Roman: PLEB
3. Padua parting: "CIAO"
4. Even though: AS MUCH AS
5. Lacks what it takes to: CANNOT
6. Equipment, in a ledger: ASSET
7. Lab rodent: RAT
8. Brainstorm: IDEA
9. Rihanna's home country: BARBADOS. Rihanna, is a Barbadian singer, songwriter, and actress.
10. Congenital: INBORN. (existing from birth)
12. Caesar's last question: "ET TU?"
13. The one over there: THAT
18. Lightweight synthetic: ORLON
22. Elite Navy fighter: SEAL. ((SEa, Air, and Land))
24. Names given to an assassin: HIT LIST
26. Rodeo automaker: ISUZU
29. Sentence subject, usually: NOUN
30. Birthday greeting opened with a click: E-CARD
31. Ewes' guys: RAMS
32. Give it __: swing hard: A RIP
33. Prep for fight night: SPAR
36. Tidies: CLEANS UP
37. Radar gun user: SPEED COP. Not a term I'm familiar with.
39. Big name in razors: ATRA
40. Rice-__: A-RONI. The San Francisco treat!
42. Airport porter: SKYCAP
43. 1986 horror film in which a man becomes an insect: THE FLY. I liked the 1958 version better.
46. Female French friends: AMIEs
47. Repast: MEAL
48. Church area behind an altar: APSE
49. Detective Wolfe: NERO
51. Roof overhang: EAVE
52. Sketch: DRAW
55. Just get (by): EKE
56. Golf Hall of Famer Ernie: ELS